How fast does mobile Internet need to be for to you give up the wired connection you're probably using right now?

Sprint's announcement of plans to expand its 4G WiMAX network reminds us that the era of predominately wired Internet connections may be coming to a close.

I see this as a parallel to people who have already given up their landline telephone to rely solely on the cellular network. In a few years, that same wireless handset might offer data connections at speeds of 100Mbps or more across wide swaths of metro areas and slower, but still mostly adequate speeds, everywhere else.

When that happens, a person might carry a single device that provides telephony and data services to meet their communications needs whether they roam--at speeds that rival today's wired connections.

It is easy to imagine a company equipping its mobile workforce with such devices. If the price is right, working from home and small remote offices could really start to empty the high-rises.

When mobile and home office connectivity is no longer second-rate, companies will find it easy to allow telepresence to become better than actually being there. Besides, there will be a lot less "there" where workers will congregate in this high-speed wireless future.

There are ways this future could become unglued, of course, and they are more likely economic than technical.

Pricing matters, both for devices and service. As does the amount of money available for network build-out. Sure, some incredibly important super-high-bandwidth application might arrive and make this next-generation mobile Internet seem as slow as wireless does today. But I don't see that happening for business users, though entertainment and gaming can be expected to overuse every resource available to them and still demand more.

I am pointedly not predicting the end of wired Internet service here.

Both businesses and homes will likely demand more than wireless can deliver, especially if they can get it at low landline prices. Yet, I believe many workers will start bringing their personal bandwidth to the office instead of connect to the office network directly.

How do we get to this future from here?

It will come in stages, with 2-4 Mbit/s WiMAX being the next plateau, then maybe 150 Mbit/s. Five years from now, we might expect gigabit wireless downlink speeds will be, if not immediately available, very close to it.

Over the next few years, we'll see WiMAX and the competing LTE (for Long-Term Evolution) technologies rolling out and speeding up. Today's WiMAX is claimed to have consistent 2-4 Mbit/s downlink speeds in Baltimore, where Sprint has been testing it. I don't know that it really matters whether WiMAX or LTE becomes the "winner" in mobile broadband.

As for Sprint's announcement, the #3 U.S. carrier said it plans to expand WiMAX into "many markets" in 2009, but only named 10. The company also didn't disclose pricing, which currently appears to be in the $80-a-month range.

If you live in one of the "many markets" slated for this year or the "multiple markets" (meaning they only named 5) scheduled for 2010, this is potentially exciting news right away.

I am, meanwhile, happy that AT&T 3G has arrived in my town, making me start to look forward to replacing my first-generation iPhone with whatever Apple presumably has planned for release this summer, to coincide with the release of the 3.0 iPhone software.

Still, seeing the Sprint announcement--WiMAX has already been the "next big thing" for way too long--points out that more mobile bandwidth is just around the corner. And I can hardly wait to start using it.